This invention relates to subterranean load-cell testing and more particularly relates to a novel and improved method and apparatus for measuring the load-bearing capacity of subterranean concrete shafts.
A previously devised method and apparatus for applying pressure and measuring upward and downward movements of the top and bottom of a load-testing device at the bottom of a concrete shaft is disclosed in my U.S. Pat. No. 4,614,110 entitled Device For Testing The Load-Bearing Capacity Of Concrete-Celled Earthen Shafts. Briefly, as set forth and described in my '110 patent, load-cell testing is carried out by placing an expansion device at the bottom of the concrete shaft and a pressurized fluid is pumped into the expansion device through a central pipe through which a telltale is inserted to measure the downward movement of the bottom of the expansion device. The telltale exits from the inside of the pressure pipe through a seal. Due to the long length of the pressure pipe, the pipe is shipped to the site in sections and must be welded in the field, and the welds must not leak under internal pressures to 8,000 psi. Once the testing has been completed, it is customary to fill the pipe and expansion device with grout by injection through the central pipe; however, it is very difficult to completely fill the pipe and expansion device without entrapping the pressurized fluid beneath the shaft.
It is therefore desirable to provide for an improved load-cell testing device of the type described which will prevent entrapment of the pressurized fluid as well as to avoid the necessity for a seal between the pipe and telltale or pressure welds in the field so as to achieve more accurate measurement of the load-bearing capacity of the shaft and assure complete filling of any voids in or beneath the shaft once the testing has been completed.